survey of Mason and Dixon Line

Between 1763 and 1767 the 233-mile (375-km) line was surveyed along the parallel 39°43′ N by two Englishmen,
Charles Mason and Jeremiah Dixon, to define the long-disputed boundaries of the overlapping land grants of the Penns, proprietors of Pennsylvania, and the Calverts, proprietors of Maryland. The dispute arose over conflicting claims to the territory from the Delaware River...